Aqueous dispersions of fluorinated polyurethanes and their use for textile coatings

ABSTRACT

Aqueous dispersions of fluorinated polyurethanes obtained by the reaction of an organic diisocyanate with a mixture of diols containing ionizable groups and macroglycols comprising polyols and at least 1% by weight of one or more hydroxy- and/or carboxy-capped fluoropolyethers. Said fluorinated polyurethanes are salified, to transform the ionizable groups into hydrophilic cations and/or anions, and are then dispersed in water to be used in textile coatings.

This application is a Continuation of application Ser. No. 137,358,filed Dec. 22, 1987, now abandoned.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present invention relates to aqueous dispersions of fluorinatedpolyurethanes and to their use for textile coatings.

More particularly, the present invention relates to aqueous dispersionsof fluorinated polyurethanes, and to their use in the preparation oftextile products endowed with both high impermeability to liquid waterand high breathability to water vapour.

2. Background of the Invention

It is well known that the textile industry has been concerned for sometime to provide textile products endowed with contemporaneously highimpermeability and breathability, for uses in the sporting field or inworking clothes, or, more generally, in clothes for open-air uses, asreported in the Journal of Coated Fabrics, 1985, 15 (7), 40-66, and inMelliand Textilberichte, 1986, 67 (4), 277-287 and 67 (11), 824-829. Forthat purpose, as these references mention, different methods are usedwhich can be divided into six main techniques.

A first technique consists in impregnating textile substrates withwater-repellent products, such as waxes, silicones, fluorinatedhydrocarbons, aluminum- and chrome-salts, and so forth. In this wayarticles are obtained which are endowed with a good breathing level, butwhich show a low impermeability, and a poor water-repellency uponwashing and wear.

A second technique comprises the coating of thick (generally thickerthan 60 g/m²) and compact layers of polyvinyl chloride, chlorinatedrubbers, polyurethanes (PU), and so forth, on textiles.

The so-obtained articles show a high impermeability, but nearly zerobreathing characteristics.

The reduction in thickness of the deposited layer, sometimes down tovalues of approximately 30 g/m², makes it possible to obtain adequatevalues of breathing characteristics but severely impairs theimpermeability.

As another alternative, microperforations are provided on heavily-coatedmaterials, e.g., by means of electrical discharges between high-voltageelectrodes, with a minor decrease in impermeability but still withinsufficient breathing characteristics.

According to a third technique, textile fabrics are coupled with filmsthat are impermeable but endowed with breathing characteristics, such asthose of polytetrafluoroethylene (PTFE) or polyester (PES).

In case of PTFE, membranes or films previously subjected to a controlleddraught, so as to provide pores of a diameter of approximately 0.2micrometers, are used. Such membranes are permeable to water vapor butnot to liquid water.

In case of PES, the breathing characteristics are secured by theformation of labile hydrogen bonds between the molecules of the watervapor and the ester functions of the fibers of the membrane from whichoccurs the transportation of water vapor between adjacent ester groups.

These articles are very satisfactory as regards the applicativeperformance, but they involve the use of expensive materials and/or of acoupling technique, less diffused and more complex than a spreading orcoating technique.

A fourth technique consists in using fabrics constituted by microfibers(having a count lower than 0.2 dtex), which are inherently hydrophobicin the absence of any treatments.

The corresponding articles have good breathing characteristics, but showconsiderable decrease in impermeability due to washings, abrasions, andsoiling with oil, or other materials, and consequently suffer serioususe limitations in the field of working clothes.

A fifth technique relates to particular coatings of two different types.One type uses polyethoxylated polyurethanes (PU's) suitable forproviding the water vapor transportation thanks to adsorptions anddesorptions following one another, according to the mechanism based onthe presence of labile hydrogen bonds, as above mentioned.

The other type uses solutions in volatile solvents of resins or monomerspolymerizable by irradiation (Chemical Week 1986, 138 (25) 22-23) andother materials suitable to develop gaseous products, e.g., isocyanicprepolymers, which develop CO₂ in the presence of moisture.

But the thus-obtained textile articles generally require furthertreatments, such as the application of silicones, or othersurface-finishing treatments.

A sixth technique provides coatings of the sponge type such as by meansof the coagulation of aqueous baths of PU's dissolved indimethylformamide, previously coated on a support fabric. This requiresrelatively complex facilities and expensive treatments of the effluentstreams. Furthermore, to achieve suitable levels of water-repellency,specific auxiliary agents are necessary, e.g., perfluorocompounds, to beintroduced into the coating formulation, or subsequently.

It has now, surprisingly, been discovered that stable aqueousdispersions of fluorinated polyurethanes, to be mainly used forpreparing textile articles endowed simultaneously with highimpermeability and good breathability, are those obtained by startingfrom an organic diisocyanate and a mixture comprising diols containingionizable groups and macroglycols based on polyols and hydroxy- and/orcarboxy-capped fluoropolyethers.

DETAILED DESCRIPTION OF THE INVENTION

The principal object of the present invention is hence the provision ofstable aqueous dispersions of fluorinated polyurethanes containing intheir macromolecule hydrophilic ionic groups, both of anionic andcationic character, which may be obtained according to the followingsteps:

(a) preparation of a fluorinated polyisocyanate, by reaction between anorganic diisocyanate and a mixture comprising diols containing ionizablegroups and macroglycols comprising polyols and at least 1% by weight ofone or more hydroxy- and/or carboxy-capped fluoropolyethers;

(b) salification of the thus-obtained fluorinated polyisocyanate, toconvert the ionizable groups into hydrophilic cations or anions; and

(c) dispersion and chain extension of the salified fluorinatedpolyisocyanate in water.

According to the present invention, the fluorinated polyisocyanate isobtained from an organic diisocyanate and a mixture on the basis ofdiols and macroglycols, in such amounts that the molar ratio of theisocyanate groups to the total sum of the hydroxy groups is within therange of from 1.2 to 2, and is preferably equal to 1.5.

The hydroxy- and/or carboxy-capped fluoropolyethers are used in amountslarger than 1% by weight, computed relative to the macroglycols, butamounts within the range of from 3 to 20% by weight are most commonlyused.

The formation of the fluorinated polyisocyanate may be carried out inthe presence or in the absence of organic solvents.

In case the reaction is carried out in the presence of solvents, thesemay be selected from the group consisting of cellosolve acetate,acetone, tetrahydrofuran, methyl ethyl ketone, and so forth.

The reaction temperatures are nearly always lower than 100° C., and arepreferably within the range of from 50° to 90° C.

The reactions may furthermore be accomplished in the presence ofcatalysts known in the art, such as the metal-organic compounds, ortertiary amines; examples of such catalysts are: dibutyltin dilaurate,tin octoate, cobalt naphthenate, vanadium acetylacetonate, dimethyltindiethylhexanoate and their mixtures, triethylenediamine,tetramethylguanidine, dimethylcyclohexylamine, and so forth. Thepreferred catalysts are triethylenediamine and dibutyltin dilaurate. Thecatalysts are used in catalytic concentrations, and generally atconcentrations not higher than 0.1% by weight.

The organic diisocyanates which may be used in the preparation of theaqueous dispersions of the present invention have the general formulaR(NCO)₂, wherein R represents an alkylene, cycloalkylene,alkylene-cycloalkylene or arylene radical containing from 1 to 20 carbonatoms.

Examples of such diisocyanates are: 2,4-toluenediisocyanate either aloneor in admixture with 2,6-toluenediisocyanate isomer,4,4'-diphenyl-methanediisocyanate,4,4'-dicyclohexyl-methanediisocyanate,1-isocyanato-3-isocyanato-methyl-3,5,5-trimethylcyclohexane (orisophorone diisocyanate), 2,4,4-trimethylhexamethylene-diisocyanate, inmixture with 2,4,4-trimethylhexamethylene-diisocyanate isomer,ethylidene-di-isocyanate, butylene-diisocyanate,hexamethylene-diisocyanate, cyclohexylene-1,4-diisocyanate,cyclohexylene-1,2-diisocyanate, xylylene-diisocyanate,dichloro-hexamethylene-diisocyanate, dicyclohexyl-4,4'-diisocyanate,1-methyl-2,4-diisocyanato-cyclohexane,1-methyl-2,6-diisocyanato-cyclohexane, and so forth. Among these, thealiphatic or cycloaliphatic diisocyanates are preferred when highresistance to U.V. light and to hydrolytic degradation are required.

As the ionizable diols, those able to endow the polyurethanicmacromolecule with a preferentially anionic charge are preferred, in asmuch as in such case end products are obtained which are compatible withauxiliary products, pigments, dyes, and aqueous dispersions of a diversenature (e.g., acrylic, vinylic, butadiene-acrylonitrilic dispersions,etc.), almost totally of an anionic nature.

As the ionizable diols, those diols may be used which contain a freecarboxyl group, preferably if bonded to the same carbon atom which bearsthe two hydroxyl groups, e.g., dimethylolacetic acid,dimethylolpropionic acid, dimethylolbutyric acid, and so forth.

Furthermore, compounds containing at least two hydroxyl groups and acarboxyl group not bound to the same carbon atom may also be used, suchas, e.g., the products of semiesterification of triols with aliphaticdicarboxylic anhydrides.

However, according to the present invention no bars exist against theuse of dispersions having a cationic character, by using as ionizablediols the tertiary alkyl-dialkanolamines already known in the art, suchas, e.g., methyldiethanolamine, butyldiethanolamine,methyldiisopropanolamine, and so forth.

The macroglycols which may be used to prepare the aqueous dispersions ofthe present invention comprise polyols and hydroxy- and/orcarboxy-capped fluoropolyethers.

As polyols, those having a molecular weight within the range of from 500to 5000, preferably of from 800 to 3000, and selected from the classconsisting of saturated polyesters, polyethers, polyester-urethanes,polyether-urethanes, polyurethaneamides, may be used.

Examples of polyesters are the products of polycondensation ofpreferably aliphatic anhydrides or dicarboxylic acids having from 4 to 9carbon atoms, such as succinic, adipic, sebacic, azelaic, etc.,anhydrides or acids with (C₂ -C₈)-aliphatic diols either alone or mixedwith one another, such as ethylene glycol, propylene glycol, 1,3- and1,4-butanediol, 1,6-hexanediol, etc., or the products ofpolycondensation of -caprolactone on diolic "starters".

Examples of polyester-urethanes are the products of polyaddition of theabove-mentioned polyesters with organic diisocyanates in molardeficiency.

Examples of polyethers are the various types of polyethylene glycol,polypropylene glycol, and, preferably, the products of polymerization oftetrahydrofuran.

The above-mentioned polyols may be used together with small amounts oflow molecular weight polyols, preferably of the trifunctional type, suchas trimethylolpropane, glycerol, 1,2,6-hexanetriol, and so forth.

The hydroxy- and/or carboxy-capped fluoropolyethers have a molecularweight within the range of from 500 to 7,000, preferably of from 1,000to 2,500, and are selected from the class of those having the formulae:##STR1## wherein: R₁ is selected from --(CH₂)_(x) --, --(CH₂ O)_(y) CH₂--, --(CH₂)_(x) OCH₂ --, wherein x and y are integers within the rangeof from 1 to 4;

m and n are integers, wherein the m/n ratio is within the range of from0.2 to 2, preferably within the range of from 0.5 to 1.2;

R_(f) is a perfluoroalkylene radical;

X is --F or --CF₃ ;

Y represents an --OH and/or a --COOH group; and

k, j, w, u, d, b, r, c, v, z, a, g are integers which make it possiblefor the above-mentioned molecular weights to be obtained.

The fluoropolyethers having the above formulae of form (I) to (IX) maybe obtained according to processes such as disclosed in U.S. Pat. Nos.3,242,218; 3,250,808; 3,665,041; 3,810,874 and 4,523,039; and inEuropean patent applications Nos. 148,482; 151,877; 165,649; and165,650.

Preferred hydroxy- and/or carboxy-capped fluoropolyethers are α,ω-bis-(hydroxymethyl)-polyoxyperfluoroalkylene and α,ω-(polyoxyperfluoroalkane)-dioic acid having an average molecular weightof 2,000, as produced and marketed by Montefluos S.p.A., under the trademarks Fomblin Z-DOL 2000 and Fomblin Z-DIAC 2000 respectively.

The salification of the fluorinated polyisocyanate, whether of anionicor cationic type, is preferably carried out in the molten state and maybe carried out by simply adding the salifying agent as such, ordissolved in water and/or solvents at temperatures of approximately 90°C.; should the molten polyisocyanate have too high a viscosity at suchtemperatures, diluting it will be suitable, before the salification,with preferably water-miscible solvents having boiling points lower thanthat of water, so as to make it possible for them to be distilled off.

The amount of solvent normally necessary does not exceed one fifth ofthe polyisocyanate weight. Examples of suitable solvents are: acetone,methyl-ethylketone, tetrahydrofuran.

For salifying the polyisocyanate of anionic type, salifying agentsselected from the class of the inorganic bases, such as sodium orammonium hydroxide, and the tertiary amines or alkanolamines, such astriethylamine, dimethylethanolamine, methyl-diethanolamine, and soforth, are preferably used.

For salifying the cationic-type polyisocyanates, organic and/orinorganic acids are used, such as hydrochloric, phosphoric, formic,lactic, acetic acid, and so forth.

After the salification is completed, the fluorinated polyisocyanate maybe dispersed in water in all dilution ratios. Therefore, the salifiedfluorinated polyisocyanate is dispersed in water so to have a solidscontent, variable according to the ionic groups, higher than 20% byweight, and preferably within the range of from 30 to 50% by weight,after the possibly previously-used organic solvent is distilled off.

According to an alternative route, the stable aqueous dispersions offluorinated polyurethanes containing in their macromolecule hydrophilicionic groups, whether of anionic or cationic nature, may be obtained bymeans of the following steps:

(i) preparation of a fluorinated polyisocyanic prepolymer by reacting anorganic diisocyanate with a mixture comprising diols containingionizable groups and macroglycols comprising polyols and at least 1% byweight of one or more hydroxy- and/or carboxy-capped fluoropolyethers;

(ii) conversion of the fluorinated polyisocyanic prepolymer into anoligo-urethane having unsaturated vinyl end groups, by reacting acompound containing hydroxyls reactive with the isocyanate groups,selected from hydroxy-alkyl-acrylates or -methacrylates having theformula: ##STR2## wherein R₂ is hydrogen or a (C₁ -C₄)-alkyl radical andW is a hydroxyalkyl radical;

(iii) salification of the so-obtained oligo-urethane to convert theionizable groups into hydrophilic cations or anions;

(iv) dispersion of the salified oligo-urethane in water; and

(v) polymerization of the unsaturated end groups of said oligo-urethanedispersed in water.

The stable aqueous dispersions of fluorinated polyurethanes containingin their macromolecule hydrophilic ionic groups are obtained, accordingto the present alternative method, according to procedures analogous tothose already disclosed.

In particular, the formation of the fluorinated polyisocyanic prepolymertakes place by the reaction between an organic diisocyanate and amixture constituted by diols and macroglycols in such amounts that themolar ratio between the isocyanate groups and the total number of thehydroxy groups is within the range of from 1.2 to 2, and is preferablyequal to 1.5.

The fluorinated polyisocyanic prepolymer is then converted into anoligo-urethane containing ethylenically unsaturated end groups, byreaction with the hydroxy-alkyl acrylates or methacrylates having theformula (X) above at temperatures lower than 150° C., and preferablywithin the range of from 60° to 120° C.

The amount of these acrylates or methacrylates used is determined by thecontent of free isocyanate groups still existing in the polyisocyanicprepolymer; such amounts, as to have NCO-eq/OH-eq ratios within therange of from 0.5 to 1.1, and preferably 1, are the most commonly used.

Preferred hydroxyl-alkyl acrylates or -methacrylates of formula (X) arethose wherein R is hydrogen, or a methyl radical, and W is a2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, or 4-hydroxybutylradical.

The thus-obtained oligo-urethane is salified and dispersed in wateraccording to the procedures disclosed above and is then polymerized byper se known techniques.

The polymerization is carried out by using free-radical generators,e.g., of the type of organic peroxides or hydroperoxides, or of the typeof sodium, potassium, ammonium persulphates, etc., either alone ortogether with such reducing agents as sodium metabisulphite, sodiumformaldehyde sulphoxylate, and so forth.

The polymerization temperature may be within the range from 10° to 100°C., according to the free radical initiator used.

The aqueous dispersions of the present invention are stable over a longtime even in the total absence of surfactants and/or protectivecolloids. Such a stability is a function of the amount of containedionic centers, which may be expressed as milliequivalents per 100 g ofpolymer, considered as the dry substance. Said values may range from 10to 60 meq/100 g of dry substance, and preferably from 20 to 40 meq/100 gof dry substance.

Because of the ionic character of the polymer, such dispersions aresensitive to electrolytes.

Stabilization thereof may be obtained by means of surfactants and/orprotective colloids of non-ionic type, such as ethoxylated derivativesof higher fatty alcohols, or alkylphenols. The use of ionic surfactantsmust obviously take into account the cationic or anionic nature of thedispersions in question.

The aqueous dispersions of fluorinated polyurethanes of the presentinvention are preferably used in the preparation or textile articlesendowed with contemporaneously high impermeability and breathability.

According to these preparation techniques, either woven or non-woventextile articles, from natural, artificial or synthetic fibers, aretreated with such dispersions by coating them on the textile article atdry-deposit levels higher than, or equal to, 20 g/m², and preferablywithin the range of from 20 to 40 g/m².

Any fibers, or fiber blends, may be used for preparing the textilearticles endowed with contemporaneously high impermeability andbreathability; examples of suitable natural fibers are wool, silk,cotton, flax, etc.; suitable artificial fibers are cellulosic fibers,and suitable synthetic fibers are acrylic, polyester, polyamidic, and soforth, fibers.

The aqueous dispersions of fluorinated polyurethanes used for thepreparation of textile articles endowed with contemporaneously highimpermeability and breathability have a solids content within the rangeof from 20% to 60% by weight, and preferably of from 30 to 50% byweight. These dispersions may be used as such, or after the addition tothem of suitable thickeners such as, e.g., cellulose ethers, polymericderivatives basded on acrylic acids and/or esters, etc.

The coating process may be performed by the usual techniques, and inparticular, by a floating knife or by a knife over roll, plate orblanket.

The degree of penetration of the coated matter into the support fabricmay be controlled by means of the viscosity of the paste, or in otherways, according to the per se known art, so as to secure the anchoringof the coating, and, at the same time, providing a proper surfacecovering.

The drying may be performed by any system which makes it possible toremove water at a temperature not higher than 100° C.; if desired,adopting expedients that accelerate water release, such as ventilation,pressure reduction, and so forth.

The usual hot-air ovens may be used, with residence times of the orderof some minutes when the air temperature is approximately 100° C.

The thus-treated textile article may be subjected to a further thermaltreatment, generally within the range of from 100° to 150° C., overshort times, to improve the fastness of the polyurethanic deposit.

By using the aqueous dispersion of the present invention, such drawbacksof the prior art as the possible treatments both before and after theapplication of the dispersion, comprising silicone application, the needfor use of impregnating or coupling techniques more complex than thecoating or of special textile articles, and so forth, may be avoided.

Furthermore, one may contemporaneously achieve high impermeability andbreathing characteristics with low levels of polyurethanic deposit, andimproved characteristics of fastness of the same deposit to both wet-and dry-washing, and, in general, to wear.

The textile articles, both woven and non-woven, after the treatment withthe aqueous dispersions of fluorinated polyurethanes of the presentinvention, have a permeability to water vapor within the range of from900 to 1600 ng/sm² Pa, as measured according to ASTM E 96, and animpermeability to water higher than 24 hours, under the 2-meter waterhead, as measured according to UNI 5122 Standard.

For the purpose of still better understanding and of practicallyembodying the present invention, some illustrative but non-limitativeexamples are given below.

EXAMPLE 1

In the preparation of a first fluorinated polyurethane, the twooperating steps were used. In the first step, an NCO-capped prepolymerwas prepared.

For that purpose, 120 g of α,ω-bis(hydroxymethyl)-polyoxyperfluoroalkylene having a molecular weightof 2,000, produced and marketed by Montefluos S.p.A. under the trademark Fomblin Z-DOL 2000; 19.7 g of toluenediisocyanate, and 60 g ofcellosolve acetate were charged, with good stirring, to a reactor filledwith nitrogen gas, connected with an expansion vessel for nitrogen, keptimmersed in a temperature-controlled bath, and equipped with stirrer,thermometer, and refluxing condenser.

After heating to 40° C., always with stirring, 0.02 g oftriethylenediamine (diazabicyclooctane, DABCO) was added, thetemperature was then increased to 80° C. and was maintained at thatvalue for approximately 2 hours, with the exothermicity of the reactionbeing monitored.

A product was obtained with a content of 70% of dry matter, with acontent of isocyanic groups of 2.4% by weight, and a molecular weight ofapproximately 2,400.

In the second operative step, the extension of the macromolecular chainand the transfer of the product into the aqueous phase were carried out.

For those purposes, to a reactor analogous to the previous one, 198.89 gof polyoxytetramethylene glycol with an average molecular weight 1,000(Terathane 1000, a product of E. I. du Pont de Nemours); 12.33 g ofdimethylopropionic acid; 22.86 g of the adduct obtained from theprevious operative step, and 64.83 g of hexamethylenediisocyanate werecharged, with the temperature being maintained first at 60° C. for 30minutes, and then at 75° C. for about 1.5 hours.

A product with 3.1% by weight of free isocyanate groups, referred to thedry substance, was obtained.

Then, 87 g of anhydrous acetone, a solution of 8.18 g ofdimethylethanolamine in 165 g of deionized water, and soon after afurther 445 g of deionized water were added.

Finally, acetone was distilled off. A milky, low-viscosity product wasobtained, which contained 31% of dry substance and 4.5% ofperfluoro-compound referred to the dry substance.

EXAMPLE 2

The process was carried out as disclosed in Example 1 until the productcontaining 3.1% by weight, relative to the dry weight, of freeisocyanate groups, was obtained. Then, 87 g was added of anhydrousacetone, with the temperature being increased to 60° C., then 5.28 g wasadded of 2-hydroxypropyl acrylate, and with the atmosphere being changedfrom nitrogen to dry air. The reaction mass was maintained at 60° C.until a content of 2.3% by weight of free isocyanate groups, relative tothe dry matter, was attained. With the reaction mass being sufficientlystirred, to it a solution of 8.18 g of dimethylethanolamine in 165 g ofdeionized water, and soon after 445 g of deionized water, were added.After the mass was dispersed in water, acetone was distilled off. Whendistillation was ended, the nitrogen atmosphere was restored, and at atemperature of 50° C., 1.19 g of tert-butyl-hydroperoxide in aqueoussolution at 12% by weight, diluted with 40 g of H₂ O, and 0.59 g ofsodium formaldehyde sulphoxylate dissolved in 40 g of H₂ O, were addedseparately within 2 hours.

A milky, low-viscosity product was thus obtained, which contained 31% ofdry substance and 4.5% of perfluoro-compound referred to the drysubstance.

EXAMPLE 3

The process was carried out in one operative step only. To a reactor,analogous to that of Example 1, 227 g of polyoxytetramethylene glycol ofthe preceding example; 13.7 g of α, ω-(polyoxyperfluoroalkane)-dioicacid having an average molecular weight of 2,000, manufactured andmarketed by Montefluos S.p.A. under the trade mark Fomblin Z-DIAC 2000;14.47 g of dimethylolpropionic acid; and 77.57 g ofhexamethylenediisocyanate, were charged with stirring.

The reaction mass was heated to 60° C. and maintained at thattemperature for 30 minutes; it was then further heated to 75° C. and wasmaintained at this temperature for 1.5 hours, whereupon a decrease inthe content of free isocyanate groups to 3.25% by weight, relative tothe dry matter, was detected.

After cooling to 60° C., 100 g of anhydrous acetone was added, then,after increasing the rate of stirring, an aqueous solution ofdimethyl-ethanolamine (10.88 g in 218 g of deionized water) was addedwithin a time of approximately 5 minutes, and soon after, a further 465g of deionized water were added.

Finally, acetone was distilled off. A milky, low-viscosity product witha content of 30% of dry substance and a level of 4% ofperfluoro-compound relative to the dry weight was obtained.

EXAMPLE 4

The process is carried out as described in Example 3, until the productcontaining 3.25% by weight, relative to the dry weight, of freeisocyanate groups is obtained.

After cooling to 60° C., 100 g of anhydrous acetone and 628 g of2-hydroxypropyl acrylate were added, and the atmosphere was changed fromnitrogen to dry air. The temperature was maintained at 60° C. until acontent of 2.2% by weight of free isocyanate groups, relative to the drymatter, was attained in the reaction mass. With an efficient stirring,to the reaction mass an aqueous solution of dimethylethanolamine (10.88g in 218 g of deionized water) was added, during a time of approximately5 minutes, and soon after a further 465 g of deionized water were added.Acetone was then distilled off.

When distillation was complete, after the nitrogen atomosphere wasrestored the temperature was increased to 50° C., and during 2 hours1.95 g of tert-butyl-hydroperoxide in an aqueous solution at 12% byweight, diluted in 30 g of water, and 0.97 g of sodium formaldehydesulphoxylate dissolved in 40 g of H₂ O were added contemporaneously, andseparately.

A milky, low-viscosity product was obtained, which contained 30% of drysubstance and a level of 4% of perfluoro-compound referred to the drysubstance.

EXAMPLE 5

An aqueous dispersion of non-fluorinated polyurethanes was prepared forcomparative purposes, by operating with the same procedures as inExample 4, but with the difference that α,ω-(polyoxyperfluoroalkane)dioic acid was not used; it was replaced by6.8 g of polyoxytetramethylene glycol.

A milky, low viscosity product was obtained which contained 30.5% of drymatter.

EXAMPLE 6

To 100 parts by weight of a dispersion obtained according to Example 1,5 parts was added of an acrylic thickening agent containing 15% byweight of dry matter.

To the resulting mixture, an aqueous solution of NH₄ OH at 32% by weightof dry matter was added, until a viscosity of 15,000 mPa sec (BrookfieldRVT at 20° C. and 20 rpm, spindle 6) was obtained.

The so-obtained coating paste was applied to a nylon fabric, whosecharacteristics are reported in Table 1, by a knife over plate. 5samples with different deposited amounts were prepared.

The coated specimens were then dried in a hot-air oven at 100° C. for 7minutes, and were then treated at 150° C. for 2 minutes inside the sameequipment.

No silicones were applied.

The finished samples were analyzed for the deposited amount (asdetermined from the difference in weight between the coated fabric andthe virgin fabric). These were then subjected to a spray test (UNI 5120)and to tests for impermeability (UNI 5122) and permeability to watervapor (ASTM E 96).

The results are reported in Table 2.

From the values of impermeability, and from the corresponding levels ofdeposited amounts, a "critical value" of the deposited amount, i.e., theminimum deposited amount for an impermeability of more than 24 hoursunder a water column of 2 meters, was evaluated.

EXAMPLE 7

By the same procedures of Example 6, but starting from the dispersionobtained according to Example 5, 7 samples of coated fabric wereprepared and subjected to the same tests, with the results summarized inTable 3.

EXAMPLE 8

By the same procedures of Example 6, but starting from the dispersionobtained according to Example 4, 5 samples of coated fabric wereprepared and subjected to the same tests, with the results as summarizedin Table 4 being obtained.

EXAMPLE 9

In order to verify their resistance to washing treatments, the samplesof Example 6 were treated in a Launder-O-Meter washing machine for 30minutes at 40° C., with detergent ECE 77 at 5 parts per thousand andwith a bath ratio of 1:20. These were then dried in air and subsequentlyat 80° C. for 10 minutes, and were finally subjected to theimpermeability test. The results are summarized in Table 5.

Neither the spray test--because it is less critical than theimpermeability test--nor the measurement of the permeability to watervapor--in that it can only improve owing to washing operations--wascarried out.

The results demonstrate the small influence of washing on theapplicative characteristics of the textile articles thus treated.

EXAMPLE 10

A further set of samples was prepared with a type of nylon analogous tothat used in the above examples, but more permeable to water vapor(permeability of 2,600 instead of 2,175 ng/s m² Pa). These samples wereprepared by operating according to the same procedures as in Example 8.

The results are reported in Table 6.

                  TABLE 1                                                         ______________________________________                                                          Unit of                                                     Characteristics   Measure    Values                                           ______________________________________                                        Chemical composition                                                                            --         nylon                                            Weight per surface unit                                                                         g/m.sup.2  65                                               Warp count        dtex       67                                               Warp filaments    --         17                                               Warp insertions   cm.sup.-1  48                                               Weft count        dtex       78                                               Weft insertions   cm.sup.-1  33                                               Weave             --         plain weave                                      Spray test        --         50                                               Impermeability (700 mm water                                                                    mm          0                                               column)                                                                       PermeabiIity to water vapor                                                                     ng/sm.sup.2 Pa                                                                           2,175                                            ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________                   Unit of                                                                             Samples                                                  Tests          Measure                                                                             1   2   3   4   5                                        __________________________________________________________________________    Deposited amount                                                                             g/m.sup.2                                                                           17   23  35  42  47                                      Spray test     --    90   90  90  90  90                                      Impermeability                                                                700 mm water column                                                                          mm    400  700                                                                               700                                                                               700                                                                               700                                                    miln  --  >10 >10 >10 >10                                      2 m water column                                                                             hours  0  >24 >24 >24 >24                                      Permeability to water                                                                        ng/s m.sup.2 Pa                                                                     1096                                                                               931                                                                               809                                                                               792                                                                               792                                     vapor                                                                         Critical deposited amount (c.d.)                                                             g/m.sup.2  20                                                  Permeability at c.d.                                                                         ng/s m.sup.2 Pa                                                                         1030                                                 __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________                   Unit of                                                                             Samples                                                                 Measure                                                                             1  2  3   4   5                                          __________________________________________________________________________    Deposited amount                                                                             g/m.sup.2                                                                            15                                                                               23                                                                               27  35  43                                        SPRAY TEST     --     50                                                                               50                                                                               50  50  50                                        Impermeability                                                                700 mm water column                                                                          mm     400                                                                             700                                                                              700 700  700                                                      min   --  2 >10 >10 >10                                        2 m water column                                                                             hours   0                                                                               0  0   0  >24                                        Permeability to water vapor                                                                  ng/s m.sup.2 Pa                                                                     1027                                                                             818                                                                              905 661  783                                       Critical deposited amount (c.d.)                                                             g/m.sup.2                                                                               40                                                   Permeability at c.d.                                                                         ng/s m.sup.2 Pa                                                                        730                                                   __________________________________________________________________________                      Unit of   Samples                                                             Measure   6  7                                              __________________________________________________________________________    Deposited amount  g/m.sup.2  47                                                                               54                                            Spray test        --         50                                                                               50                                            Impermeability                                                                700 mm water head mm         700                                                                              700                                                             min       >10                                                                              >10                                            2 m water head    hours     >24                                                                              >24                                            Permeability to water vapor                                                                     ng/s m.sup.2  Pa                                                                         705                                                                              774                                           Critical deposited amount (c.d.)                                                                g/m.sup.2                                                   __________________________________________________________________________

                  TABLE 4                                                         ______________________________________                                                   Unit of   Samples                                                  Tests      Measure   1      2     3    4    5                                 ______________________________________                                        Deposited amount                                                                         g/m.sup.2 17     28     31   38   53                               Spray test --        80     80     80   90   90                               Impermeability                                                                700 mm water                                                                             mm        250    700    700  700  700                              column                                                                                   min       --     >10   >20  >10  >10                               2 m water column                                                                         hours      0     >24   >24  >24  >24                               Permeability                                                                             ng/s m.sup.2 Pa                                                                         879    914    887  922  757                              to water vapor                                                                Critical deposited                                                                       g/m.sup.2        20                                                amount (c.d.)                                                                 Permeability                                                                             ng/s m.sup.2 Pa  910                                               at c.d.                                                                       ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                                     Units of  Samples                                                Tests        Measure   1     2    3    4    5                                 ______________________________________                                        Impermeability after                                                                       hours     0     >24  >24  >24  >24                               washing                                                                       2 m water column                                                              ______________________________________                                    

                                      TABLE 6                                     __________________________________________________________________________                 Unit of                                                                             Samples                                                    Tests        Measure                                                                             1   2   3   4   5                                          __________________________________________________________________________    Deposited amount                                                                           g/m.sup.2                                                                           12   27  36  45  54                                        Spray test   --    80  80/90                                                                             80/90                                                                             80/90                                                                             80/90                                      Impermeability                                                                70 mm water column                                                                         mm    150  700                                                                               700                                                                               700                                                                               700                                                    min   --  >10 >10 >10 >10                                        2 m water column                                                                           hours  0  >24 >24 >24 >24                                        Permeability to water                                                                      ng/s m.sup.2 Pa                                                                     1024                                                                              1027                                                                              1001                                                                               948                                                                               879                                       vapor                                                                         Critical deposited amount                                                                  g/m.sup.2                                                                           20                                                         (d.c.)                                                                        Permeability at d.c.                                                                       ng/s m.sup.2 Pa                                                                     1130                                                       __________________________________________________________________________

Although the invention has been described in conjunction with specificembodiments, it is evident that many alternatives and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, the invention is intended to embrace all ofthe alternatives and variations that fall within the spirit and scope ofthe appended claims.

What is claimed is:
 1. Stable aqueous dispersions of fluorinated polyurethanes containing in their macromolecules hydrophilic ionic groups, both of anionic and cationic character, obtained by the process comprising the steps:(a) preparing a fluorinated polyisocyanate, by reaction between an organic diisocyanate and a mixture comprising diols containing ionizable groups and macroglycols comprising polyols and at least 1% by weight of one or more hydroxy- and/or carboxy-capped fluoropolyoxyalkylene ethers; (b) salifying the so-obtained fluorinated polyisocyanate, to convert the ionizable groups into hydrophilic cations or anions; and (c) dispersing and chain extending the salified fluorinated polyisocyanate in water.
 2. Aqueous dispersions according to claim 1, wherein the molar ratio between the isocyanate groups to the sum of the hydroxyl groups is within the range of from 1.2 to
 2. 3. Aqueous dispersions according to claim 2, wherein the molar ratio between the isocyanate groups to the sum of the hydroxyl groups is 1.5.
 4. Aqueous dispersions according to claim 1, 2 or 3, wherein the macroglycols comprise from 3 to 15% by weight of one or more hydroxy- and/or carboxy-capped fluoropolyoxyalkylene ethers.
 5. Aqueous dispersions according to claim 1, 2 or 3, wherein the hydroxy- and/or carboxy-capped fluoropolyoxyalkylene ethers have a molecular weight within the range of from 500 to 7000, preferably of from 1000 to
 2500. 6. Aqueous dispersions according to claim 1, 2 or 3, wherein the hydroxy- and/or carboxy-capped fluoropolyoxyalkene ethers are selected from the class consisting of those having the formulae: ##STR3## wherein: R₁ is selected from --(CH₂)_(x) --, --(CH₂ O)_(y) CH₂ --, --(CH₂)_(x) OCH₂ --, wherein x and y are integers within the range of from 1 to 4;m and n are integers, wherein the m/n ratio is within the range of from 0.2 to 2, preferably within the range of from 0.5 to 1.2; R_(f) is a perfluoroalkylene radical; X is --F or --CF₃ ; Y represents an --OH and/or a --COOH group; and k, j, w, u, d, b, r, c, v, z, a, g are integers which make it possible for the above-mentioned molecular weights to be obtained.
 7. Aqueous dispersions according to claim 6, wherein the hydroxy- and/or carboxy-capped fluoropolyoxyalkylene ethers are α, ω-bis-(hydroxymethyl)-polyoxyperfluoroalkylene and α, ω-(polyoxyperfluoroalkane)-dioic acid, with an average molecular weight of 2,000.
 8. Stable aqueous dispersions of fluorinated polyurethanes containing in their macromolecule hydrophilic ionic groups, of either anionic or cationic nature, obtained by the process comprising the following steps:(i) preparing a fluorinated polyisocyanate prepolymer by reacting an organic diisocyanate with a mixture comprising diols containing ionizable groups and macroglycols comprising polyols and at least 1% by weight one or more hydroxy- and/or carboxy-capped fluoropolyoxyalkylene ethers; (ii) converting of the fluorinated polyisocyanic prepolymer into an oligo-urethane having unsaturated vinyl end groups, by reacting a compound containing hydroxyl reactive with the isocyanate groups selected from the class consisting of hydroxy-alkyl-acrylates or -methacrylates having the formula: ##STR4## wherein R₂ is hydrogen or a (C₁ -C₄)-alkyl radical and W is a hydroxyalkyl radical; (iii) salifying of the so-obtained oligo-urethane to convert the ionizable groups into hydrophilic cations or anions; (iv) dispersing the salified oligo-urethane in water; and (v) polymerizing the unsaturated end groups of said oligo-urethane dispersed in water.
 9. Aqueous dispersions according to claim 8, wherein the hydroxyalkyl-acrylates or -methacrylates are those wherein R is hydrogen or a methyl radical, and W is a 2-hydroxyethyl-, 2-hydroxypropyl-, 3-hydroxypropyl- or 4-hydroxybutyl-radical.
 10. Aqueous dispersions according to claim 8, wherein the hydroxyalkyl-acrylates or -methacrylates are used in such a an amount as to have NCO-eq/OH-eq ratios, to the free isocyanate groups present in the polyisocyanic prepolymer, within the range of from 0.5 to 1.1, preferably equal to
 1. 11. Aqueous dispersions according to claim 9, wherein the hydroxyalkyl-acrylates or -methacrylates are used in such an amount as to have NCO-eq/OH-eq ratios, to the free isocyanate groups present in the polyisocyanic prepolymer, within the range of from 0.5 to 1.1, preferably equal to
 1. 12. Aqueous dispersions according to claim 1, 2 or 3, wherein the salified fluorinated polyisocyanate dispersed in water having a content of solids higher than 20% by weight, preferably within the range of from 30 to 50% by weight.
 13. Aqueous dispersions according to claim 1, 2 or 3, wherein the fluorinated polyurethanes contain in their macromolecule ionic groups in an amount within the range of from 10 to 60 milliequivalents per 100 g of polymer, preferably of from 20 to 40 meq/100 g of polymer. 